LA County has the highest number of cross-county commuters.  From Reuters

(Reuters) - About 600,000 Americans are megacommuters who work at least 50 miles from home and take at least 90 minutes to get there, with the biggest concentration in California, the U.S. Census Bureau said on Tuesday.

The agency said the percentage of Americans who travelled at least 90 minutes to work daily has inched higher in the last two decades even as the number of people who work from home has soared by 45 percent.

The average one-way daily U.S. commute is 25.5 minutes, and one in four commuters leave their home counties for work, the Census Bureau said, based on its annual American Community Survey.